Commander Keen - Heart of Darkness is a fan game made in Game Maker by DrColossus. It is a 2.5D crossover between Commander Keen and Heart of Darkness.
This one level demo is loosely leaned on the first section of the original Heart of Darkness game. The main character is replaced by the Commander Keen sprite.

Game Play

Commander Keen - Heart of Darkness is a cinematic platformer in which the player controls Commander Keen, who faces various dangers. Through the game's linear storyline the player progresses by navigating various environments and solving puzzles, all whilst attempting to keep Commander Keen from being killed by evil shadows, hungry wildlife, and perilous obstacles.
Gameplay Video: https://www.youtube.com/watch?v=AHiCSaGdRK8

Technical Information

The ground is a 3D Object with a EGA texture. The sprites graphics were recorded scene by scene and then extracted in Photoshop. The generated 3D environment were processed via trial and error.